[Ord. No. 39-1998, § 6.1.1, 12-1-1998]
The following are general standards based on the type of drainage system in existence in the development area:
(1) 
Urban systems. Drainage facilities located within the bypass of the City shall include an enclosed underground system capable of effectively removing stormwater and groundwater from the street and adjacent areas. Discharge of drainage shall be into natural drainage courses or approved connection to an existing system capable of handling the increased flow. Direct connections to existing combined sewer systems is prohibited. Applicants for development requiring storm drain systems will be required to pay the cost of extending the storm drain system to the site if such extension is possible. If conditions warrant, and upon approval of the City engineer and/or code enforcement officer, the Planning Board may allow a combination of rural and urban drainage standards or utilize rural standards entirely.
(2) 
Rural systems. Drainage facilities located within areas defined by this chapter as rural may, if approved by the City engineer, consist of a system of culverts and open drainage channels capable of effectively carrying stormwater into natural drainage courses and dewatering the roadway subgrade.
(3) 
Urban and/or rural systems. Drainage facilities located within areas defined by this chapter as urban and/or rural shall comply with subsections (1) and (2) of this section, as appropriate.
[Ord. No. 39-1998, § 6.1.2, 12-1-1998]
(a) 
Generally.
(1) 
A drainage system plan is required. See chapter 102.
(2) 
Stormwater management plans shall show means whereby the peak discharge for the developed site shall not exceed the peak discharge for the undeveloped site for the two- and twenty-five-year storms. Emergency spillways shall be provided for storms in excess of the twenty-five-year storm.
(3) 
In the case of major subdivisions, street drainage shall be designed to detain stormwater through a number of means, with detention ponds as a last resort. All runoff entering the street drainage system from proposed lots shall not exceed the pre-development rate of runoff.
(4) 
Pipe inlet and outlet invert elevations shall be shown on the profiles of the drainage plan. Catchbasin inlet grate elevations shall be shown on the plans.
(5) 
All drainage systems within the development shall be designed to meet the criteria of the performance standards for a twenty-five-year storm based on rainfall data as available. Flows shall be computed by appropriate methods, with design computations being submitted for review by the City engineer and the highway superintendent. Other agencies may have different requirements.
(6) 
Upstream drainage shall be accommodated by an adequately sized drainage system through the proposed development for existing and future potential development in the upstream drainage area or areas tributary to the proposed development.
(7) 
Existing upstream and downstream drainage facilities shall be studied to determine the effect of the proposed development's drainage. The developer shall demonstrate to the satisfaction of the City engineer that the storm drainage from the proposed development will not, in any way, overload or damage existing storm drainage systems upstream or downstream from the proposed development.
(8) 
Where open ditches (other than street-side ditches), channels, streams, or natural drainage courses are used to collect, discharge, and/or transmit water through the development, an adequately sized, perpetual drainage easement shall be provided. The easement shall be centered as closely as possible to the middle of the watercourse and shall be no less than 30 feet in width in order to allow adequate ingress and egress for maintenance equipment.
(9) 
Where a drainage easement is to contain an open ditch, channel, stream or natural drainage course, the following shall apply:
a. 
The easement shall be cleared of all trees and brush and all stumps shall be removed to the extent necessary to allow adequate drainage and to provide vehicular access for maintenance where determined necessary.
b. 
The channel shall be constructed according to a plan which will show the following:
1. 
The location and boundaries of the easement.
2. 
Contour lines depicting the shape and slope of the channel.
3. 
Typical cross section of the channel showing how the channel will be constructed to prevent erosion.
(10) 
Drainage easements shall be private, and adequate care and maintenance of the easements shall be a provision of the deeds and covenants of the respective private properties on which the easements are located unless otherwise permitted by the Planning Board.
(11) 
No clean water (stormwater) will be allowed to connect into any sanitary sewer system.
(b) 
Urban systems.
(1) 
Underdrain shall be installed on both sides of curbed streets, unless the base can drain to a ditch. Type C underdrain systems are allowed with appropriate design considerations, and approval of City engineer. The City engineer may approve the installation of underdrain on only the uphill side of the street on streets traversing a slope or on only one side of the street in relatively flat areas if the developer's engineer can demonstrate that the street area surface water infiltration will be quickly drained from the street aggregate base/subbase and that groundwater will not reach the street aggregate base/subbase once the development is fully developed.
(2) 
The minimum pipe size for closed conduit systems shall be eight inches in diameter, and the minimum size shall be 15 inches in diameter for open systems, except for type B underdrain pipe, which may be six inches in diameter.
(3) 
The design of storm drains shall be on the basis of flowing full at a minimum velocity of 2.5 feet per second.
(4) 
Three hundred fifty feet shall be considered as the maximum length for carrying stormwater in a street gutter to an intake at a catchbasin otherwise approved by the City engineer or the highway superintendent.
(5) 
Catchbasin inlet grate elevations shall be recessed two inches below gutter line grades.
(6) 
No water shall be permitted to drain across a street or an intersection.
(7) 
Catchbasins or manholes shall be placed at all vertical and horizontal changes in the alignment or pipe, and at all junctions. However, in no case shall catchbasins or manholes be placed at intervals exceeding 350 feet, unless otherwise approved by the City highway superintendent.
(8) 
A minimum of four feet of cover is required over the tops of all storm drain pipe, or frost protection must be provided subject to the approval of the code enforcement officer or City engineer.
(9) 
House foundation perimeter drains and roof drains with backflow check-valves may be connected to the storm drainage system upon written approval by and under the supervision of the highway superintendent.
(c) 
Rural systems.
(1) 
Streetside ditches and outlet channels shall be of a configuration and size to carry the contributory stormwater and subsurface flows from the streetway structure and streetside embankments. In all instances, the invert of the ditch shall be a minimum of six inches below the subgrade of the streetway extended to the shoulder, except as follows:
a. 
In areas of well-drained native soils, when approved by the City engineer; or
b. 
In areas where subsurface soils are of a nature requiring an underain system, in which case subgrades may be constructed to direct subsurface water to the storm drain system.
(2) 
Ditches shall drain in a positive manner.
(3) 
Streetside ditches shall be at a minimum grade of 1.5% or the grade required to handle the design flow, whichever is greater, unless otherwise approved by the City engineer. Grades between the minimum stated and 0.5% will be allowed only if strict construction control is adhered to, and as approved by the City engineer.
(4) 
Ditch linings shall be provided to protect the side slopes and bottom from erosion and scour. Minimum channel linings for corresponding longitudinal slopes shall conform to the following table:
0.5%—3.0%
Loam and seed
3.0%—6.0%
Loam and seed, protected by erosion control mesh
6.0%—8.0%
Sod placed over loam
Over 8.0%
Stone, masonry or bituminous concrete
(5) 
Standards for culverts are as follows:
a. 
Cross culverts. Culverts crossing under roads or streets shall be sized to pass a twenty-five-year frequency storm from the contributing drainage area with a maximum hydrostatic head of two feet above the culvert inlet invert or three inches below the outside edge of the shoulder, whichever is the greater elevation.
b. 
Driveway culverts. Culverts shall be installed under any proposed or existing driveway that interrupts the natural or proposed longitudinal drainage along any street or road. Driveway culverts shall be of a size capable of passing a ten-year frequency storm from the contributing drainage area with a maximum hydrostatic head as specified in subsection (c)(5)a of this section. Driveway culverts shall be ADS or equal, unless otherwise approved by the director of public works, and have a minimum diameter of 12 inches. The final determination of the culvert size shall be made by the City engineer. Driveway culverts shall be installed on the grade of the streetside ditch line.
c. 
Minimum cover. The minimum cover over culverts in the roadway areas shall be 24 inches. The minimum cover over driveway culverts shall be 12 inches.
d. 
Ditch lines. Street-side ditch lines shall be extended laterally and lowered to accommodate culverts with inlet and/or outlet inverts below the normal grade of the ditch line.
(d) 
Drainage system materials. The following materials shall be utilized for drainage system construction and shall conform to criteria established by the City highway superintendent and the City engineer, and sanitary district specifications:
(1) 
Reinforced concrete pipe. Concrete pipe shall be class IV reinforced concrete pipe meeting ASTM designation C-76.
(2) 
PVC pipe. All PVC pipe shall meet the requirements of SDR-35 of ASTM specification D-3034.
(3) 
Corrugated metal pipe. Corrugated metal pipe and fittings shall be plain galvanized, aluminum or bituminous coated conforming to the requirements of MDOT specifications, section 707 (Metallic Pipe). Pipe gauge shall be as required to meet soil and traffic loads with a deflection of not more than 5%.
(4) 
Underdrain. Pipe for underdrain shall be perforated PVC-SDR-35 meeting the requirements of ASTM specification D-3034.
(5) 
Manholes.
a. 
Manholes shall be precast concrete sections conforming to ASTM C478.
b. 
Manhole steps shall be polypropylene plastic, M.A. Industries PS2-PF-SL or equal. The spacing between the steps shall be 12 inches.
c. 
The manhole frame and cover shall be Etheridge No. E265S or equal. Covers shall be marked "Drain."
d. 
Manholes shall have a minimum inside diameter of four feet in the barrel section and two feet in the cone or top slab ingress/egress opening.
e. 
Manhole inverts shall be constructed of hard brick meeting federal specification SS-B-656 and shaped to the crown of the pipe.
f. 
All openings in the manhole for receiving pipe shall have a neoprene boot meeting ASTM C-443.
(6) 
Catchbasins.
a. 
Catchbasins shall be pre-cast concrete sections conforming to ASTM C478.
b. 
Cast iron catchbasin frames and grates shall be Lebaron type F, Etheridge type M or equal.
c. 
Catchbasins shall have a minimum two-foot sump for the retention of waterborne solids.
d. 
Catchbasins shall have a minimum inside diameter of four feet in the barrel section and two feet in the cone or top slab ingress/egress opening.
e. 
All openings in the catchbasin for receiving pipe shall have a neoprene boot meeting ASTM C-443.
(e) 
Installation of drainage systems.
(1) 
Drainage system construction shall conform to all City standards.
(2) 
All trenching shall be accomplished in accordance with all appropriate state and federal safety standards.
(3) 
The maximum trench width at the pipe crown shall be the outside diameter of the pipe plus two feet.
(4) 
Pipe, excluding culvert pipe, shall be bedded in three-quarter-inch screened stone with a minimum depth of six inches below the pipe. The top of the stone shall be to the top of the pipe or above. A minimum of 12 inches of cover sand shall be placed over the top of the pipe. When the excavated trench bottom is not sufficiently firm to properly support the pipe, the City engineer may direct the developer to excavate below grade to suitable foundation material and backfill with additional three-quarter-inch screened stone.
(5) 
All gravity pipe shall be laid with a laser device designed for the purpose unless other means are approved by the City engineer.
(6) 
All catchbasins and manholes shall be founded below the frost line on a minimum depth of six inches of three-quarter-inch screened stone compacted to a uniform density.
(7) 
All drain outlets shall be terminated with riprap to prevent erosion. Facilities for energy dissipation shall be provided. Culvert pipe inlets shall be constructed so as to prevent or decrease damage to embankments and/or to improve the efficiency of the culvert. Inlet control devices shall be approved by the planning board.
(8) 
Type B underdrain (six-inch diameter, for intercepting groundwater) shall be laid with the perforations down on a minimum six-inch bed of three-quarter-inch screened stone. The three-quarter-inch screened stone shall be brought to a point 12 inches above the top of the underdrain pipe. The remainder of the trench to the bottom side of the subgrade of the road shall be backfilled with clean granular material.
[Ord. No. 39-1998, § 6.1.3, 12-1-1998]
(a) 
Generally. Chapter 102 outlines the intent and applicability of the standards in this section.
(b) 
Performance standards.
(1) 
Erosion land sediments shall be controlled through appropriate management practices to prevent adverse downstream water quality impacts. Hydraulic calculation techniques and design standards for facilities to achieve this performance standard shall be of accepted methods and subject to approval of the code enforcement officer and City engineer.
(2) 
Natural and manmade drainageways and drainage outlets shall be protected from erosion from water flowing through them. Drainageways shall be designed and constructed in order to carry water from a twenty-five-year storm or greater, and shall be stabilized with vegetation or lined with riprap.
(c) 
Control measures to apply during all stages of activity. Erosion and sedimentation control measures shall apply to all aspects of the proposed project involving land disturbance, and shall be in operation during all stages of the activity. The amount of exposed soil at every phase of construction shall be minimized to reduce the potential for erosion.
(d) 
Maintenance of facilities. The developer shall maintain all components of the erosion and sediment control and stormwater management system unless the system is formally accepted by the City, or sanitary district or is placed under the jurisdiction of a legally created property owners' association whose charter and powers require maintenance of the system, including adequate financing to carry out this responsibility.
(e) 
Stabilization timelines.
(1) 
In general, all activities regulated by these standards shall be conducted after March 1 and before October 30 unless accomplished in conjunction with approved construction.
(2) 
Disturbed soil shall be stabilized within one week from the time it was last actively worked using temporary or permanent measures such as placement of riprap, sod, mulch or erosion control blankets, or other comparable measures.
(3) 
In all cases within the shoreland zones, permanent stabilization shall occur within nine months of the initial date of exposure.
(4) 
Fill sites shall be graded and seeded within 30 calendar days of their closure or by October 31 (whichever date occurs first). Fill sites may remain open after October 31 only by written permission of the code enforcement officer.
(5) 
Permanent revegetation of all disturbed areas, using native plant material wherever possible, shall occur:
a. 
Within 30 days from the time the areas were last actively worked;
b. 
For spring and summer activities, by October 31; or
c. 
For fall and winter activities, by June 15, except where precluded by the type of disturbance (e.g., riprap, road surfaces, etc.). The vegetative cover shall be maintained.
(f) 
Adaptation to existing topography. In order to create the least potential for erosion, development shall be designed to fit with the topography and soils of the site. Areas of steep slopes where high cuts and fill may be required shall be avoided wherever possible, and natural contours shall be followed as closely as possible.
(g) 
Anchoring of mulch. If mulch is likely to be moved because of steep slopes or wind exposure, it shall be anchored with netting, peg and twine, or other suitable method and shall be maintained until a catch of vegetation is established over the entire disturbed area.
(h) 
Prevention of sedimentation of water. In addition to placement of riprap, sod, erosion control blankets or mulch, additional steps shall be taken, where necessary, in order to prevent sedimentation of the water. Evidence of sedimentation includes visible gully erosion, discoloration of water by suspended particles and slumping of banks. Silt fences, staked hay bales and other sedimentation control measures, where planned for, shall be in place prior to commencement of work, but shall also be installed whenever necessary due to sedimentation.
(i) 
Maintenance of temporary control measures. Mulch or other temporary erosion control measures shall be maintained until the site is permanently stabilized with vegetation or other permanent control measures.
(j) 
Application of mulch. Where mulch is used, it shall be applied at a rate of at least one bale per 500 square feet and shall be maintained until a catch of vegetation is established.
(k) 
Disposal of excavated materials. Any and all excavated material shall be removed to approved locations. The City shall provide a list of approved sites within the City limits.
[Ord. No. 39-1998, § 6.1.4, 12-1-1998]
The checklist of required submissions relative to this article is as follows:
(1) 
Map submissions.
a. 
Location map with boundaries of the development clearly marked.
b. 
USGS topographic map, or larger-scale map when available or if necessary for clarification, with boundaries of the site clearly marked and drainage areas used for stormwater management calculations noted. Predevelopment drainage areas shall be noted. Post-development drainage areas shall be noted.
c. 
Topographic maps specifically for the project with:
1. 
Pre-development contours noted.
2. 
Post-development contours noted.
3. 
Limits of clearing and grading noted.
4. 
Location of stormwater control structures.
5. 
Location of sediment and erosion control practices.
6. 
Pre-development drainage patterns noted.
7. 
Post-development drainage patterns noted.
8. 
Flow lengths used in time-of-concentration calculations noted.
d. 
SCS medium intensity soils map with boundaries of the development clearly marked and drainage areas used for stormwater management calculations noted.
e. 
High-intensity soil survey for the development site.
(2) 
Narrative submissions.
a. 
Description of the development, which shall:
1. 
Describe the nature of the development.
2. 
Describe present and post-development land use cover.
3. 
Describe which areas will be disturbed by construction.
4. 
Describe adjacent areas which will be disturbed by construction.
5. 
Describe areas on-site especially vulnerable to erosion.
6. 
Describe the soils found on-site.
b. 
Description of stormwater handling, which shall include the following:
1. 
Summary and analysis of existing stormwater movement.
2. 
Analysis of post-development stormwater movement.
3. 
Methods being proposed to control stormwater.
The method of calculation shall be noted.
c. 
Description of erosion and sedimentation control, which shall list and describe the practices and structures to be used and shall:
1. 
Indicate how accelerated erosion will be minimized.
2. 
Indicate how sedimentation will be minimized.
d. 
Schedule of construction, including a schedule of installation/implementation of temporary and permanent sediment and erosion control structures and management practices.
e. 
Description of inspection and maintenance for sediment and erosion control measures.
(3) 
Design drawings and calculations.
a. 
Detail drawing of any structural practices used that are not referenced.
b. 
Calculations for stormwater management practices, which shall include the following:
1. 
Worksheets, showing assumptions used.
2. 
Detention basins.
3. 
Culverts.
4. 
Ditches and waterways.
5. 
Other calculations.
c. 
Calculations for sediment and erosion control practices, which shall include the following:
1. 
Worksheets.
2. 
Sediment basins.
3. 
Diversions.
4. 
Ditches and waterways.
5. 
Other calculations.
[Ord. No. 39-1998, § 6.1.5, 12-1-1998]
Resource publications (current revisions) for preparing erosion and sediment control plans are as follows:
(1) 
The Maine Erosion and Sediment Control Handbook for Construction, prepared by the state department of environmental protection.
(2) 
Stormwater Management Manual, prepared by the Greater Portland Council of Governments.
(3) 
Technical Release 55, Urban Hydrology for Small Watersheds, R-55, June 1986, available from National Technical Information Service NTIS, U.S. Department of Commerce, Springfield, VA 22161, (703) 487-4650 (TR 20 may also be used).
(4) 
Other publications, subject to approval of the stormwater management board.
(5) 
Maine Erosion and Sediment Control Handbook for Construction Best Management Practices, prepared by Cumberland SWCD and the state department of environmental protection.
[Ord. No. 39-1998, § 6.1.6, 12-1-1998]
General criteria for sediment and erosion control plans are as follows:
(1) 
All denuded areas shall be stabilized.
(2) 
All soil stockpiles shall be stabilized.
(3) 
Permanent vegetation shall be established.
(4) 
Adjacent properties shall be protected from sediment from the development.
(5) 
Adjacent properties shall not be subjected to erosion due to increased runoff water from the development.
(6) 
Cut and fill slopes shall be constructed and stabilized in a way to reduce erosion.
(7) 
On-site waterways and outlets shall be stabilized.
(8) 
Storm sewer inlets shall be protected from sediment.
(9) 
If working in or crossing live streams, they shall be protected during construction.
(10) 
Construction access routes shall be stabilized to include dust control.
(11) 
Temporary sediment and erosion control structures shall be removed when the development is finished.
(12) 
Maintenance of stormwater, sediment, and erosion control structures shall be addressed adequately.
[Ord. No. 39-1998, § 6.1.7, 12-1-1998]
(a) 
Riprap. MDOT specifications, section 610 (Stone Fill, Stone Blanket and Stone Ditch Protection), shall be applicable to this subject.
(b) 
Erosion control blankets. MDOT specifications, section 613 (Erosion Control Blankets), shall be applicable to this subject.
(c) 
Sodding. MDOT specifications, section 616 (Sodding), shall be applicable to this subject.
(d) 
Loam. MDOT specifications, section 615 (Loam), shall be applicable to this subject. All esplanades, circular turnaround islands, ditch slopes, and other planting strip areas at the sides of streets shall receive at least four inches of loam.
(e) 
Seeding. MDOT specifications, section 6.18 (Seeding), shall be applicable to this subject. Seeding method number 1 (Park Mixture) shall be used on areas specified in subsection (d) of this section.
(f) 
Mulch. MDOT specifications, section 619 (Mulch), shall be applicable to this subject.
(g) 
Geotextiles. MDOT specifications, section 620 (Geotextiles), shall be applicable to this subject.
(h) 
Landscaping. MDOT specifications, section 621 (Landscaping) and section 622 (Transplanting Shrubs, Hedges and Trees), shall be applicable to this subject.
(i) 
Dust control. MDOT specifications, section 637 (Dust Control), shall be applicable to this subject. Dust control shall be provided for all areas as necessary to prevent the visible emissions of dust in the air.